Cat >file << EOF

1, cat >file record is keyboard input, equivalent to create a file from the keyboard, and can only create new files, cannot edit existing files. > is a data redirection that outputs the text content you enter into file.

2. Cat <<eof

The cat command is a text output command under Linux, usually for viewing the contents of a file;
EOF is "End of File", which represents the text terminator.

Combining these two identities avoids the use of multi-line echo commands and results in multiple lines of output.

"Example" # #------> Use cat > File <<eof to implement output from multiple lines of files

Cat > Ip.txt << EOF
124
42131341
7879879879
32114
Eof

3. Cat > Ip.txt

Abcd
Dcba
Eftf
Ctrl-d

Cat >file << EOF